Amateur astronomers from Shoalhaven Australia

Tag Archives: Astronomy

Last month, Professor Ron Ekers present a free lecture at Curtin University to commemorate the publishing of the discovery of Quasars.

I’m please to let you know we’ve got the final edit of the “Quasars – from the Milky Way to the Edge of the Universe with Prof Ron Ekers” up on youtube and ready to be share with anyone who would be interested.

“On March 16th, 50 years ago, a joint effort between Australia and the USA led to the discovery of Quasars and fundamentally shifted our thinking about the Universe. This is a fascinating story of scientific debate, monumental leaps in knowledge, and global cooperation.

Professor Ron Ekers speaks about what we’ve learned over the past 50 years of peering into space and where we might go next with telescopes such as the Square Kilometre Array.

Professor Ekers has worked with some of the world’s most renowned astronomers at some of the top University’s and Observatories including Cal Tech and the National Radio Astronomy Observatory in New Mexico.

He was elected a Fellow of the Australian Academy of Science, a Foreign Member of the Royal Dutch Academy of Science, a Foreign Member of the American Philosophical Society and a Fellow of the Royal Society. He’s a past President of the International Astronomical Union (IAU) and a member of the Advisory Board for the Peter Gruber Foundation Cosmology Prize.”

If you are interested in Astronomy and have often wondered how you could learn more, the Duke University is offering a free course via an on-line medium called Coursera.

This innovative educational network of Universities providing free courses from a broad range of subjects and topics. The Coursera web site describes themselves as “…a social entrepreneurship company that partners with the top universities in the world to offer courses online for anyone to take, for free. We envision a future where the top universities are educating not only thousands of students, but millions. Our technology enables the best professors to teach tens or hundreds of thousands of students.Through this, we hope to give everyone access to the world-class education that has so far been available only to a select few. We want to empower people with education that will improve their lives, the lives of their families, and the communities they live in.”

The course that is of the greatest interest to us is the “Introduction to Astronomy” course provided by Duke University, North Carolina. In this class, “we will be studying, quite literally, everything in the universe. We will start with “classical” astronomy, describing the night sky and organizing what we see as was done in ancient times. We will then embark on a journey, starting here on Earth and progressing outward, to study the Solar system, the Milky Way galaxy, and the wonderful and strange objects we observe in deep space, such as black holes, quasars, and supernovae. We will end with some discussion of what scientists know today about the universe as a whole. Along the way we will introduce some of the methods, theoretical and experimental, that have been used to understand all of this, from Newton’s laws, through our understanding of light and matter, to Einstein’s theory of relativity, and from Galileo’s telescope to WMAP.”

This nine week course is 100% on-line making it accessible to virtually everyone who has access to the internet. Requiring a medium level of mathematical and physics knowledge is the only prerequisite, with a certificate of completion offered at the successful completion of the course. The availability of free education is quickly becoming a thing of the past. With Coursera offering this opportunity for free education world wide there is an incentive for many students and would be students to continue further education throughout their life.

Solar Eclipse: Northern Queensland

14th November 2012

On 14th November 2012, Australia will again experience the shadow of the moon as it passes between the Sun and the Earth. This event (second contact) will occur at 20:38UT on November 13th which translates to 6:38 am Australian Eastern Standard Time on 14th November due to the difference in the time zones.

The first point of contact for the shadow will be in the Northern Territory on the north east boarder of Kakadu National Park near Ubirr Rock. The path of the shadow will continue east across Arnhem Land, crossing the Gulf of Carpentaria then onto the Cape York peninsula near Wallaby Island. From here the shadow will progress south east crossing the eastern coast of Queensland 30 km north of Cairns.

Cairns and Port Douglas will provide some of the best viewing areas as they are populated tourist destinations providing ample accommodation and services. At the time of totality, the sun will have risen 14° above the horizon when it will last for two minutes.

As sunrise on the day will be approximately 5:35am, there is an hour available to find the best location for your observation point. there is the option to drive up or down the coast to find the best location north of Port Douglas, where their are open fields and places to stop with many other eclipse chasers. This require a bit of planning the day before as an early start in the dark will make it difficult to see what the cloud cover looks like. My suggestion is to find a comfortable spot on the balcony of your Resort room with a hot breakfast delivered to your room. All-in-all, coast observers might be better advised to sit and take whatever nature offers, as no matter what decision you make it will be just as good as any other on the day.

A total solar eclipse forms a rare opportunity to observe the corona (the outer layer of the Sun’s atmosphere). Normally this is not visible because the photosphere is much brighter than the corona. According to the point reached in the solar cycle, the corona may appear small and symmetric, or large and fuzzy. It is very hard to predict this prior to totality.

Phenomena associated with eclipses include shadow bands (also known as flying shadows), which are similar to shadows on the bottom of a swimming pool. They only occur just prior to and after totality, when a narrow solar crescent acts as an anisotropic light source

When the shrinking visible part of the photosphere becomes very small, Baily’s beads will occur. These are caused by the sunlight still being able to reach Earth through lunar valleys. Totality then begins with the diamond ring effect, the last bright flash of sunlight.

It is safe to observe the total phase of a solar eclipse directly only when the Sun’s photosphere is completely covered by the Moon, and not before or after totality. During this period the Sun is too dim to be seen through filters. The Sun’s faint corona will be visible, and the chromosphere, solar prominences, and possibly even a solar flare may be seen. At the end of totality, the same effects will occur in reverse order, and on the opposite side of the Moon.

Under normal conditions, the Sun is so bright that it is difficult to stare at it directly. However, during an eclipse, with so much of the Sun covered, it is easier and more tempting to stare at it. In fact however, looking at the Sun during an eclipse is as dangerous as looking at it outside an eclipse, except during the brief period of totality, when the Sun’s disk is completely covered (totality occurs only during a total eclipse and only very briefly; it does not occur during a partial or annular eclipse). Viewing the Sun’s disk through any kind of optical aid (binoculars, a telescope, or even an optical camera viewfinder) is extremely hazardous and can cause irreversible eye damage within a fraction of a second.

Looking directly at the photosphere of the Sun (the bright disk of the Sun itself), even for just a few seconds, can cause permanent damage to the retina of the eye, because of the intense visible and invisible radiation that the photosphere emits. This damage can result in impairment of vision, up to and including blindness. The retina has no sensitivity to pain, and the effects of retinal damage may not appear for hours, so there is no warning that injury is occurring.

Photographing an eclipse is possible with fairly common camera equipment. In order for the disk of the Sun/Moon to be easily visible, a fairly high magnification long focus lens is needed (at least 200 mm for a 35 mm camera), and for the disk to fill most of the frame, a longer lens is needed (over 500 mm). As with viewing the Sun directly, looking at it through the viewfinder of a camera can produce damage to the retina, so care is recommended.

Star Stuck

Has the rain stopped? It didn’t even rain at Easter (except in Sydney somewhere, and Melbourne of course). Cool dry evenings and the end of daylight savings mean you can get out observing quite early. The lack of dust and moisture in the air make observing conditions excellent, while the lack of heat means turbulence is minimal. If you can brave the cold, the next six months are the best time of year for amateur observers.

So, what’s happening? Firstly don’t forget there is a Transit of Venus on June 6th. If anyone wants to get some advice about observing the Sun safely please contact me on markab@westnet.com.au More immediately the best planet for us to view is beautiful Saturn. Saturn transits the meridian on April 16th (due north at local midnight) and is rising around sunset. As such, Saturn is perfectly placed for viewing throughout the night. With a modest telescope and medium magnification you should be able to see the shadow of the rings on the planet and perhaps even the dark ring dividing the two bright rings known eloquently as the A ring and B ring. Who says astronomers have no imagination? This is known as the Cassini division after its discovery in 1675 by Giovanni Domenico Cassini. The rings can even be seen in 10x binoculars if they are mounted on a tripod or held steadily. Saturn has five moons that may be seen in progressively larger telescopes but even binoculars will allow us to find Titan, which is actually the largest of all moons in the solar system, having a diameter of 5,152 klms. Saturn resides in the constellation Virgo for all of 2012 and is currently just north of the 1st magnitude star Spica, αVirginis. Spica will appear quite white and Saturn very yellow. There are few other bright stars in this area but Mars is just over the border in Leo near the bright star Regulus. Mars will appear a rusty orange colour and Regulus more yellow-white. Regulus marks the resting foreleg of Leo, the mythical Lion. Mars is actually shining brighter than Saturn but is quite small. I would be interested to hear of anyone perceiving any detail on this enigmatic planet.

For the deepsky observers, Virgo and the adjacent constellation Leo are veritable goldmines of galaxy fields. As a matter of fact a supernova was discovered on March 16th in the galaxy M95 in Leo. Currently this end of life stellar explosion is shining with the light of 500 million Suns! It is still invisible to the naked eye and actually happened 38 million years ago, its light only reaching us just now. M95 is part of a well known trio of galaxies with, M96 and M105, all visible in one low power field. Its coordinates are RA 10 44m Dec =11° 42’

Above we see an image of the entire galaxy field in Leo taken by my friend Bob Price from Bethanga, in Victoria. Six galaxies appear in total with one unnamed. M95 is in the bottom right of the image with the SN showing just below to the right and some glare from nearby Mars bleeding into the pixels from the right.

This SN and galaxy is easily visible in a 150mm telescope and Leo is currently in our north, about 35° up the sky.

Although they are the natural result of the end of life cycle of a massive star, supernovae are relatively rare. Only three are known to have occurred in our Milky Way in the last 1000 or so years. The first occurred in Taurus and was recorded by Chinese and Middle Eastern astronomers around 1054 A.D. It’s remnant is the famous Crab Nebula, M1. The next was discovered and observed in 1572 by the Danish Astronomer Tycho Brahe, in the constellation Cassiopeia, it became known as Tycho’s Star.

Below: Tycho’s Star as recorded in his observing notes. It is designated I and called Nuoa Stella, New Star. As you can see it appeared very bright

The most recent was SN 1987a in the Large Magellanic Cloud (strictly speaking not in our galaxy but in our galactic neighbourhood). It was actually discovered by radio astronomers, three hours ahead of being discovered visually, simultaneously in Chile and New Zealand.

It is now a brilliant planetary nebula with the typical hourglass shape created by the expanding rings of gas shown end on.

The Transit of Venus

What is it that makes an event in nature special? Is it the rarity of its occurrence, the immensity and sheer wonder of the spectacle, or possibly the effect it has on mankind? There are arguments for all these criteria and there is also personal significance. There will be a Transit of Venus on June 6th this year and while it is
not a visual spectacle that excites the imagination of the general populace the way a Total Solar Eclipse does, it is an event that holds great significance for us all.
Firstly, it is a truly rare event. Transits of Venus occur in pairs eight years apart but then do not recur for 105.5 years and on the next cycle 121.5 years. Total Solar Eclipses occur at the rate of three every two years. Few people alive to see this transit will see another. Transits of Venus were unknown until Johannes Kepler, the great planetary mathematician, predicted an occurrence on December 6th, 1631. Venus appears as a small round black dot when crossing the face of the Sun, invisible to the naked eye. As Galileo had turned the newly invented telescope on the heavens for the first time in 1609 it had never been observed before. Due to a small error in parallax mathematics Kepler did not predict the second of the transit pair occurring eight years later but it was independently predicted and observed by English amateur Jeremiah Horrocks on 4 December 1639. As he was not well known and did not publicise his calculations it is believed he and his friend were the only two people on the planet to see this one.

Right – The Author’s photo of the Jun 8, 2004 Transit
In the eighteenth century, advances in telescope design and instrumentation continued at breakneck speed. Planetary positions and orbits were plotted more accurately and predictions could be mathematically refined. Around this time we see the great nations of Europe exploring the world by sea for trade riches and power. The Spanish, French, English, Dutch and Portuguese had been sending explorers to all corners of the globe for a hundred years. Enormous riches and influence, not to mention new territories to claim, were the spoils for the adventurous, however many of these explorers and crew perished because they became lost. Unable to accurately ascertain their longitude they could miss their target by many miles or hundreds of miles, running out of water and food or becoming becalmed in unknown waters. It was easy to find your latitude, simply measure the angle of the Sun above your horizon at local noon but to find your longitude was more difficult. The story of the search for the best method is brilliantly told by Dava Sobel in her book Longitude. If a navigator could know accurately the time at a given point on the globe, say Greenwich or Paris, he could compare it to noon at the meridian of his location.

Every hour difference was equal to 15 degrees of longitude. Many solutions were proposed but ultimately those who had accurate timepieces, unaffected by temperature, barometric pressure or the motion of a ship, would be the most astute navigators. The chronometer and its use for accurately plotting one’s position was obviously a momentous advance for mankind but what has it got to do with the Transit of Venus? As you will see both our own history and the development of astronomy are connected by this event.
After observing a transit of Mercury in 1677, the brilliant English astronomer, Sir Edmund Halley, proposed that the next transit of Venus could be used to determine the distance of Venus from the Sun, and by simple trigonometry the distance from Earth to the Sun.

Why was this important to astronomy?

Astronomers had noticed that some stars, when measured at different times of the year, appeared to move slightly against the background stars. They had known of this effect for quite some time as the superior planets (outside Earth’s orbit) would appear to move in reverse against the stellar background for a short period when Earth went past them in its own orbit. This effect was known as parallax. See the diagram below.

By checking a stars position at six monthly intervals an astronomer would be measuring the baseline of a triangle the diameter of Earth’s orbit or twice the length of the Earth – Sun distance. Knowing that distance accurately meant the parallax distance to some stars and perhaps measurement of the scale of the visible universe would be within their grasp.

Above: The transit appears differently from separate locations on Earth – (courtesy of Exploratorium TV)
Halley proposed to use a smaller measure of parallax to find this Venus-Sun/ Earth-Sun distance. He posited that two observers timing the Transit from distant locations on Earth could create a long enough baseline using parallax measures to create a heoretical angle from Earth through Venus to the Sun. Johannes Kepler, who formulated the three Laws of Planetary Motion, had also calculated, with his third Law, the ratio of a planets distance from the Sun compared to the time taken for its orbit. Kepler had proven that the ratio of Venus’ distance to the Sun compared to Earth was 0.72. By multiplying the apparent Venus /Sun angle by 0.72 we arrive at the Earth/Sun angle. Let’s not worry about the actual equation here but remember we have now worked out the angle and the length of one side of our triangle (the distance between our observers on Earth) and we can use our High School maths (remember Sine, Cos and Tan?) to calculate the distance accurately. This method is the same as used by all surveyors to determine distance with a theodolite.

Diagram of the Timing of a Transit – (courtesy of Quasar Publishing)

Of course, unless the observers in different parts of the world knew their positions accurately they could not determine the distance between each other. Most of the advanced seafaring powers and their respective scientific societies equipped and commissioned Transit expeditions to all corners of the globe. This is where our recent history and the event of the Transit

Venus black drop effect

intersect. For the Transit of 1769 the English Navy purchased a coal carrying ship called the Earl of Pembroke , and joined with the Royal Society in commissioning a Research survey to Tahiti and the South Pacific. As it was nominally a Naval vessel it could only be commanded by a ranking Naval officer so James Cook, chosen for his navigational skills and his surveying prowess,
was duly promoted to Lieutenant and commissioned to observe the Transit of Venus from Tahiti on June 3, 1769. As the Commander of the ship he was entitled to be called Captain. From Tahiti Cook was to continue to New Zealand to observe a Transit of Mercury on 9 November and map the North and South islands while there. Here he was to open his sealed orders that instructed him to continue west where he discovered and mapped the east coast of Australia. On this first tour of duty Cook navigated with the use of accurate Moon and star charts supplied by the Royal Observatory at Greenwich, using a sextant to calculate angles and lunar distance. On his second voyage of discovery in 1771 he had the benefit of a replica of Harrison’s famous
chronometer to calculate his longitude, but no Transit to time on this occasion. This chronometer cost £400 or approximately £59,000 in today’s currency.
When all the timing, positional, and angular measures were calculated the results from the earlier Transit of 1761 and those of 1769 gave a figure for the Earth/Sun distance that only varied from our modern measure by about 3%. Inaccuracies crept in because of poor seeing, poor timing, poor calculation of locations, and an anomalous effect of the Transit known as the Black Drop that made it difficult to see the exact second the planet entered or exited the disc of the Sun. Around a century later in 1874 and 1882, the research was conducted primarily with the new technique of photography but was again slightly marred by the discovery that Venus had an atmosphere which generated further inaccuracies in timings.

So, is the event rare? It certainly is! Is it an immense and wondrous spectacle? Perhaps only when you consider the implications. Does it have a profound effect on mankind? The event itself, perhaps not, but the observation generated an enormous tide of activity in the affairs of men. It pressured advances in technology, navigation, timekeeping, measurement and the science of Astronomy. Is it personally significant? To us, who will not see another, it may be. If you have an inkling of the history it must affect you. Personally, it is one of many aspects of the Universe above our Earth that astonish and compel me.
Clear Skies.

As we go to press I can confidently state there has not been one clear night this year, well not clear enough to get a scope out anyway. While it hasn’t been raining every day it’s certainly been cloudy most evenings so the observing log is just about empty.
I have been doing a bit of solar observing but even that has been on hold during early February. The Sun is very active with multiple and large sunspots as well as high solar flare activity. Has this got something to do with the big wet events or the big snows in Europe? Who knows? If the weather gives a chance to observe later this month try observing Jupiter very early in the evening, in the west. The seeing will be poor for detail but as I explained at the January meeting there are quite a few Jupiter Moon events occurring at decent hours throughout February. Most of these can be seen in twilight so check the times on pp 112-113 of Astronomy 2012. The New Moon occurs on 22nd February so maybe it will coincide with better viewing conditions. Jupiter is setting around 930pm toward the end of February and by the end of March Jupiter will be only visible in twilight as it heads behind the Sun. Jupiter is not the brightest “star” in the west in the evening, that mantle belonging to Venus, shining at magnitude -4.2 ! Next month I will write a brief article on the Transit of Venus occurring in June and give a small presentation at the March Club Meeting.
Saturn, in Virgo this year, is rising at about the time Jupiter is setting (around 930pm mid February) and will become the planetary target of choice by March. As with most objects you need to wait about an hour after they rise to get decent viewing. The sky moves 15° every hour and 15° is about the minimum clearance from the horizon before the seeing becomes passable.

This is mainly due to the extra atmosphere we need to penetrate close to the horizon. The ring plane is gradually opening and will be at the greatest tilt by December but Saturn, if it is available, is the “go to” object for any observing session. At every public viewing I’ve ever attended I’ve always heard people say, “It doesn’t look real”. Hard to believe it is 1.4 billion kilometres from the Sun.

Saturn as it appears in a small telescope

As Autumn approaches the Milky Way has wheeled right over and deep sky observers begin to look out into the great void above our galaxy. Without countless billions of stars obscuring our vision we can search for all those faint galaxies in the rich constellations of Leo, Virgo and Coma Berenices, to name a few. I suggest that if you are a new observer or have a telescope with aperture around
200mm or 8- inch that you start off with the Messier objects. These are marked on any star map with a capital M followed by a number. Messier was a comet hunter who plotted these objects so that he could avoid them and not mistake them for comets in his nightly sweeps. As his equipment was of inferior quality to that which is used today he was unable to see enough detail to guess at their true nature.

His favorite telescope was a 7-1/2 inch Gregorian reflector. They are good targets because they are generally brighter than most deep sky objects. While the All Sky maps in your almanac display the M objects it would be better to use a basic star atlas like the Pocket Sky Atlas. Some of the more famous are M1 – the Crab Nebula, M42 – the Orion Nebula, M104 – the Sombrero Galaxy, M57 – the Ring Nebula. Messier has an impressive resume and there is a good biographical sketch of Messier at the following link: http://messier.seds.org/xtra/history/biograph.html